The use of synthetic vascular grafts to replace or bypass diseased vessels is a common surgical procedure, but graft failure occurs often and is primarily due to thrombosis and/or intimal/anastomotic hyperplasia. The hypothesis of this proposal is that extracellular matrix (ECM) molecules of the pseudointima and interstitial tissues of vascular grafts in humans inhibit the adhesion, proliferation and migration of cells, particularly endothelium. This lack of endothelialization may result in activation of coagulation or complement cascades and platelet and leukocyte adhesion/activation eventually leading to thrombosis. The ECM molecules in conjunction with growth factors may promote smooth muscle or myofibroblast growth leading to anastomotic hyperplasia. The experimental approach will involve an evaluation of adsorbed proteins or molecules in the pseudointima or interstitial tissue from retrieved human vascular grafts by immunological and in situ hybridization techniques. Emphasis will be placed on coagulation, fibrinolytic or complement proteins for surface evaluation and collagens, proteoglycans and RGD peptide containing molecules for in situ hybridization analysis. A significant portion of the proposal will involve a comprehensive analysis, in vitro, of some of the more important ECM molecules and their interactions with vascular cells on clinically used, candidate and reference biomaterials. Studies will include protein adsorption, cell adhesion, proliferation and migration with these ECM molecules coated onto various surfaces. In addition, cells cultured on these matrices will be exposed to physiologic shear stress and flow, two aspects that may be particularly important to vascular graft pathophysiology. Biochemical characterization of molecules such as type V collagen, heparin/heparan sulfate and coagulation factors, will address issues regarding potential mechanisms related to cellular growth proliferation and/or inhibition as well as studies involving matrix molecule interactions. These interaction studies will correlate to the situation occurring in vivo, that is, a complex molecular environment. Thus, studies involving both in vitro and in vivo analysis and their correlations will aid in more fully understanding the pathology of vascular grafts. Therefore, the overgoal of this project is directed toward obtaining a better understanding of the mechanisms related to healing events occurring on and within human vascular grafts.